For the purpose of improving fuel consumption and reducing knocking or exhaust emissions, an internal combustion engine for a vehicle, which is provided with an EGR device that recirculates a portion of exhaust gas as an EGR gas to an intake passage, has been proposed.
However, in an internal combustion engine having an EGR device mounted therein, even though an EGR valve is closed when a throttle valve closes at the time of deceleration, EGR gas may remain within an EGR passage or an intake passage on a downstream side of the EGR valve. In particular, in a system that recirculates EGR gas to an intake passage on an upstream side of a throttle valve, a large amount of EGR gas may remain within the intake passage on the upstream side of the throttle valve. For this reason, a combustion state may deteriorate due to an excessive increase in the amount of EGR gas flowing into a cylinder at the time of deceleration and a subsequent re-acceleration. As a result, a misfire is likely to occur.
To solve such a problem, for example, as disclosed in a patent document (JP 2013-11271 A), a cylinder-inflow EGR gas amount of an internal combustion engine is estimated, and a misfire limit EGR gas amount is calculated on the basis of an operation state of the internal combustion engine. Then, the misfire limit EGR gas amount is compared with the cylinder-inflow EGR gas amount to predict whether a misfire may occur. When it is predicted that the misfire may occur, misfire avoidance control (e.g., fuel injection amount increase control) is executed to avoid the misfire.
However, in a system that provides deceleration by delaying an ignition timing of an internal combustion engine at the time of deceleration (i.e., by increasing an ignition timing delay amount) to decrease torque, a misfire limit is decreased when delaying the ignition timing at the time of deceleration. For this reason, even when the above-described misfire avoidance control is executed, the effects for avoiding a misfire may be insufficient depending on deceleration conditions, resulting in failing to avoid the misfire. Whereas, when the amount of EGR gas is decreased in order to avoid the misfire, fuel efficiency effects through EGR gas may deteriorate.